This invention relates to an apparatus for treating the surface of articles such as foils, plates or molded articles by electric brush discharge, which apparatus comprises a first electrode for guiding the articles to be treated and at least one facing brush electrode having a quartz coating, which can be connected to opposite potential and is cooled by a cooling air flow flowing over the outside thereof.
Such an apparatus is known from German Offenlegungsschrift No. 2,550,810. The efficiency of the known apparatus is limited by the fact that in the case of a too high operating voltage a breakdown occurs between the electrodes instead of the desired shower of sparks and the apparatus is held automatically switched off. This effect is aided by the fact that the electrical conductivity of the quartz coating of the brush electrode increases with increasing quartz temperature. If the quartz coating is hotter at one point that in the remaining area, the energy exchange is concentrated at this point. It therefore gets hotter and a breakdown rapidly occurs leading also to a minute hole in the quartz coating and consequently to the deterioration thereof.
It has been found that the efficiency of such apparatus can be significantly increased if a good cooling of the active discharging side of the brush electrode is ensured.